Experimental Study On The Ultrasonic Doppler Based Measurement Of Underwater Leakage Bubble Velocity

The seepage is a widespread natural phenomenon in marine environment. Seabed seep activity and methane leakage not only caused the complex marine biogeochemical and ecological processes, but also occupies an important position in the study of global carbon cycle and climate effect; Leakage gas turn into natural gas hydrate in suitable environment,which could be the future energy. It is necessary to observe the seabed seep, in order to detect the leakage of gas flow of natural gas.The seepage velocity of bubbles is the main parameter measurement of gas flow rate of the leakage seabed seep. In order to observe the leakage of cold gas flow in-situ, the article is the basis of the method of steady bubble state before measurement and leakage bubble flow measurement by transmission acoustic wave, carried out on the basis of experimental study on Ultrasonic gas fraction and optical bubble flow rate, a new method that is proposed to measure the leakage of the bubble flow rate, application of ultrasound Doppler measure the seepage velocity of bubbles by two the principle of Doppler effect and measurement of bubble Doppler ultrasound.This article introduces the theory of the Doppler ultrasound, scattering and reflection law of sound waves, as well as the fast FFT transform. In order to verify the correctness of method that ultrasonic Doppler measure the seepage bubble velocity, the design of the sending and receiving of ultrasonic Doppler flow measurement device is based on the principle of ultrasonic Doppler, reflection and scattering of acoustic,by preliminary experiment,the Doppler frequency shift can calculate the seepage velocity of bubbles.Then on the basis of improvement to eliminate the problem of the angle of bubble movement direction and ultrasonic beam,and to optimum structure, experiment study of the way of one sending and two receiving. The experimental device can simulate different submarine seepage gas bubbles flow,can measure seabed seep bubble velocity by ultrasonic Doppler,and can measure in three position by the Doppler device of the swing angle. Study on the relationship between bubble velocity and different seabed seep gas flow,experiment results show that the regular of different gas flow on the seabed seep and bubble velocity,and the influence of angle swing on the measurement results.